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In this paper, we describe synthesis and characterization of YVO 4 and Eu 3+ -doped YVO 4 nanopowders. Two methods of preparation were used—solution combustion synthesis (SCS) and classical ceramic method (CCM)—and compared. Morphology and structure of all samples were characterized with atomic-force microscopy (AFM), X-ray diffraction (XRD), and field-emission scanning electron microscopy (SEM). Raman spectroscopy was used to discuss the isotope-like effect. It is confirmed that doping with Eu ions results in a change of Raman spectra of doped samples—new modes arise, and intensity of existing ones change. Influence of different preparation methods on isotope-like effect is presented with detailed calculations of shifted modes. © 2019 John Wiley & Sons, Ltd.

In the present work experimental study of the ZnO@ZnS core-shell nanostructure with an active layer obtained by conversion of zinc oxide powders with H2S is reported. Тhe prepared structures were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and far-infrared spectroscopy. Top surface optical phonon (TSO) in ZnO, characteristic for the cylindrical nano-objects, the surface optical phonon (SOP) mode of ZnS, and SOP modes in ZnO@ZnS core-shell nanostructure are registered. Local mode of oxygen in ZnS and gap mode of sulfur in ZnO are also registered. This result is due to the existence of an active layer in the space between ZnO core and ZnS shell, which is very important for the application of these materials as thermoelectrics. © 2020 John Wiley & Sons, Ltd.

Structural and optical properties of CdTe thin films were investigated applying atomic force microscopy (AFM), XRD powder technique, Raman spectroscopy and far–infrared spectroscopy. CdTe thin films were prepared by using thermal evaporation technique. In the analysis of the far – infrared reflection spectra, numerical model for calculating the reflectivity coefficient for system which includes films and substrate has been applied. Effective permittivity of film mixture (CdTe and air) was modeled by Maxwell – Garnet approximation. We reveal the existence of surface optical phonon (SOP) mode and coupled plasmon-SOP modes (CPSOPM).

The analysis of the vibrational properties of mechanochemically synthesized stannite Cu2FeSnS4 nanocrystals has been performed. X-ray diffraction (XRD) and Raman spectroscopy are techniques used to characterize the crystal structure and compositional purity of stannite Cu2FeSnS4 nanoparticles. The detailed analysis of the experimental spectra has allowed us to determine the frequency and symmetry assignment of the main and weaker peaks. The milling time influence on synthesis stannite Cu2FeSnS4 from elemental precursors Cu, Fe, Sn and S is observed. Among the peaks that are characteristic for the stannite Cu2FeSnS4, we registered the modes of binary phases of FeS and SnS. The total disappearance of the binary phases of FeS and SnS is observed when the milling time is longer than 90 min.

The Raman spectra of Eu3+ doped Gd2Zr2O7 nanopowders were measured. We registered three phonons at 177 cm−1, 268 cm−1, and 592 cm−1, as well as their overtones at 354 cm−1, 445 cm−1, 708 cm−1, 1062 cm−1, 1184 cm−1, ∼1530 cm−1, and ∼1720 cm−1. The phonon at 592 cm−1 is known to be characteristic for Gd2Zr2O7 fluorite-type structure; however, the other two have not been registered so far. We found that the position of the newly detected phonons agrees well with the observed electron-phonon interaction. On the other hand, the registered multiphonon processes were a consequence of miniaturization that further induced changes in electronic structure of Eu3+ doped Gd2Zr2O7 nanopowders.

The polymer nanocomposite ZnS/Poly (methylmethacrylate) was prepared by the solution casting method and its structural and optical properties were investigated using XRD, SEM, TEM, HRTEM , and Raman spectroscopy . The basic material, ZnS , has the cubic structure and its crystallite size was estimated to be 2.3 nm, which implies that a strong confinement regime is in effect. Analysis of Raman spectra was performed using the fitting procedure based on effective medium theory. As a result, the surface optical phonon (SOP) mode was detected. It was found that the shape and position of the SOP mode depend on the type of the composite.

CdGeAs 2 is a promising material for optical applications. It has the wide transparency range between 2.3 and 18 μm except harmful absorption region at 5.5 μm. Its presence is related to the crystal lattice quality. The measurements of Raman and far infrared reflectivity spectra of the series of Cd 1− x Mn x GeAs 2 samples (0 ≤ x ≤ 0.037) were carried out in spectral range from 60 to 400 cm −1 , at room temperature. Beside all expected optical modes three defect modes are registered at about 125, 170 and 235 cm −1 . Their intensities are related to tetragonal distortion of lattice (Δ) so we connected them with lattice defects Ge As , usually formed in this material, and CdAs 2 and Cd 3 As 2 clusters whose characteristic frequencies match these values. Antisite defects Ge As are connected to energy level at about 200 meV and to absorption at 5.5 μm. Based on obtained results we can conclude that doping with small amount of manganese ( x = 0.004) results in slight deformation of CdGeAs 2 crystal lattice and consequently considerably reducing the formation of antisite defects Ge As .

Nanocrystalline samples of ZnO(Mn) were synthesized by hydrothermal method. The morphology of the samples was studied by HRTEM and SEM. X-ray diffraction was used to determine composition of the samples (ZnO and ZnMn2O4) and the mean crystalline size (from 16 to 99 nm). In this paper we report the experimental spectra of Raman scattering (from 100 to 1600 cm−1) with surface optical phonons (SOP) in range of 497–538 cm−1 as well as formation of new phases MnO, Mn3O4 and ZnMnO3. The phonon of registered phase's exhibit effects connected to phase concentration, while the SOP phonon mode exhibit significant confinement effect.

The nanopowders of (ZnO)1–x(Al2O3)x, where x ranges from 0 to 0.7, were obtained by two chemical methods: the co-precipitation/calcination and hydrothermal synthesis. The first assessment of structural and optical properties of the obtained nanopowders was undertaken by the SEM, XRD, Raman and far-infrared spectroscopy, which was followed by the photoluminescence spectroscopy at room temperature. The obtained far-infrared reflectivity spectra were analyzed using the fitting procedure. The dielectric function of ZnO–Al2O3 nanopowders was modeled by the Maxwell-Garnet formula under the assumption that the nanopowders are a mixture of homogenous spherical inclusions in air. The combined plasmon-LO phonon modes (CPPM) were observed in the far-infrared reflection spectra. The photoluminescence spectra contain emissions related to the presence of ZnO, ZnAl2O4, and AlOOH phases in the nanomaterial, which is in agreement with the results obtained by other experiments.

Nanocrystaline samples of ZnO(Fe) were synthesized by traditional wet chemical method followed by calcinations. Samples were characterized by X-ray diffraction to determine composition of the samples (ZnO, ZnFe 2 O 4 and Fe 2 O 3 ) and the mean crystalline size (from 8 to 51 nm). In this paper we report the experimental spectra of Raman scattering (from 200 to 1600 cm −1 ) with surface optical phonons (SOP) in range of 500–550 cm −1 . The phonon of registered phase’s exhibit effects connected to phase concentration, while the SOP phonon mode exhibit significant confinement effect.

Properties of CdS thin films were investigated applying atomic force microscopy (AFM) and Raman spectroscopy. CdS thin films were prepared by using thermal evaporation technique under base pressure 2 x 10-5 torr. The quality of these films was investigated by AFM spectroscopy. We apply Raman scattering to investigate optical properties of CdS thin films, and reveal existence of surface optical phonon (SOP) mode at 297 cm-1. Effective permittivity of mixture were modeled by Maxwell - Garnet approximation. [Projekat Ministarstva nauke Republike Srbije, br. 45003]

Nanocrystalline samples of ZnO(Mn) were characterized by X-ray diffraction to determine composition of the samples (ZnO, Mn3O4, ZnMn2O4 and ZnMnO3) and the mean crystalline size (between 9 and 13 nm for ZnMnO3 phases, from 24 to 47 nm for Mn3O4 phases and above 100 nm for ZnO and ZnMn2O4 phases). In this paper we report the experimental spectra of Raman scattering (from 200 to 1600 cm−1) with surface optical phonons (SOP) in range of 520–575 cm−1. The phonon of registered phases exhibits effects connected to phase concentration, while the SOP phonon mode exhibits significant confinement effect.

Our work deals with the problem of producing a complex metal-ceramic composite using the processes of internal oxidation (IO) and severe plastic deformation. For this purpose, Cu-Al alloy with 0.4wt.% of Al was used. IO of sample serves in the first step of the processing as a means for attaining a fine dispersion of nanosized oxide particles in the metal matrix. Production technology continues with repeated application of severe plastic deformation (SPD) of the resulting metalmatrix composite to produce the bulk nanoscaled structural material. SPD was carried out with equal channel angular pressing (ECAP), which allowed that the material could be subjected to an intense plastic strain through simple shear. Microstructural characteristics of one phase and multiphase material was studied on internally oxidized Cu with 0.4wt.% of Al sample composed of one phase copper-aluminum solid solution in the core and fine dispersed oxide particles in the same matrix in the mantle region. In this manner AFM, X-ray diffraction and Raman spectroscopy were used. Local structures in plastically deformed samples reflect presence of Cu, CuO, Cu2O, Cu4O3 or Al2O3 structural characteristics, depending on type of sample. [Projekat Ministarstva nauke Republike Srbije, br. III45003]

Nano spinel ferrites MFe2O4 (M=Ni, Mn, Zn) were obtained by soft mechanochemical synthesis in a planetary ball mill. The appropriate mixture of oxide and hydroxide powders was used as initial compounds. All of this mixture of powders was mechanically activated, uniaxial pressed and sintered at 1100°C/2h. The phase composition of the powders and sintered samples were analyzed by XRD and Raman spectroscopy. Morphologies were examined by SEM. In this study, the AC-conductivity and DC-resistivity of sintered samples of MFe2O4 (M= Ni, Mn, Zn) ferrites were measured at different frequencies and at room temperature. The values of the electrical conductivities show an increase with increasing temperature, which indicated the semiconducting behavior of the studied ferrites. The conduction phenomenon of the investigated samples could be explained on the basis of hopping model. The complex impedance spectroscopy analysis was used to study the effect of grain and grain boundary on the electrical properties of all three obtained ferrites [Projekat Ministarstva nauke Republike Srbije, br. III 45003]

The properties of 3 monolayers (ml) CdTe self-assembled quantum dot (SAQD) sample are investigated by means of Raman and photoluminescence (PL) spectroscopy. The PL spectrum is characterized by two main emission peaks, both connected with the existence of QDs. One presents direct deexcitation to ground state and the other one is optical phonon ( ω = 204.2 cm −1 ) assisted deexcitation. One-phonon Raman spectra at room temperature show surface-optical phonon at 201 cm −1 . At temperatures below 200 K, multiphonon processes are registered. Multiphonon maximum depends on the temperature, and laser energy.

Two zinc ferrite nanoparticle materials were prepared by the same method – soft mechanochemical synthesis, but starting from different powder mixtures: (1) Zn(OH) 2 /α-Fe 2 O 3 and (2) Zn(OH) 2 /Fe(OH) 3 . In both cases a single phase system was obtained after 18 h of milling. The progress of the synthesis was controlled by X-ray diffractometry (XRD), Raman spectroscopy, TEM and magnetic measurements. Analysis of the XRD patterns by Rietveld refinement allowed determination of the cation inversion degree for both obtained single phase ZnFe 2 O 4 samples. The sample obtained from mixture (1) has the cation inversion degree 0.3482 and the sample obtained from mixture (2) 0.400. Magnetization measurements were confirmed that the degrees of the inversion were well estimated. Comparison with published data shows that used method of synthesis gives nano powder samples with extremely high values of saturation magnetizations: sample (1) 78.3 emu g −1 and sample (2) 91.5 emu g −1 at T = 4.5 K.

The properties of CdS thin films were investigated by applying atomic force microscopy (AFM), Raman and far-infrared spectroscopy. CdS thin films were prepared by using the thermal evaporation technique under base pressure 2 × 10 −5 torr. The quality of these films was investigated by AFM spectroscopy. We applied Raman scattering and far-infrared spectroscopy to investigate the optical properties of CdS thin films, and reveal the existence of Surface Optical Phonon (SOP) mode at 297 cm −1 . Effective permittivity of mixture was modeled by Maxwell–Garnet approximation. In the analysis of the far-infrared reflection spectra, a numerical model for calculating the reflectivity coefficient for a system which includes films and substrate was applied.

Bismuth germanium oxide Bi12GeO20 (BGO) has very interesting electrical, optical and magnetic properties. In order to make devices based on this material more flexible, its powder was used for preparing polymer composites. This study reports investigation of the effects of using different solvents and polymers in preparation of BGO composite on the microstructural and optical behaviour of the resulting material. Preparation of such composites by a solution casting method is described. Poly (methyl methacrylate) (PMMA) and polystyrene (PS)) were used as matrix materials and acetone and chloroform as solvents. Their microstructure and the quality of BGO dispersion and deaggregation in polymer matrix were analyzed by SEM, Raman, XRD and optical spectroscopy. The influence of particle size distribution, their shapes, and concentration on the optical transmission is calculated based on Mie scattering theory and discussed, too. This is the peer-reviewed version of the article: Brajovic, L.M., Stojanovic, D.B., Mihailovic, P., Markovic, S.B., Romcevic, M., Mitric, M., Lazovic, V., Dramlic, D., Petricevic, S., Romcevic, N., 2017. Preparation and characterization of bismuth germanium oxide (BGO) polymer composites. Journal of Alloys and Compounds 695, 841–849. [https://doi.org/10.1016/j.jallcom.2016.10.140]

This paper describes the structural and optical properties of Cu-Se-CuSe2 thin films. The surface morphology of thin films was investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Formation of thin films is concluded to proceed unevenly, in the form of islands which later grew into agglomerates. The structural characterization of Cu-Se-CuSe2 thin film was investigated using X-ray diffraction pattern (XRD). The presence of two-phase system is observed. One is the solid solution of Cu in Se and the other is low-pressure modification of CuSe2. The Raman spectroscopy was used to identify and quantify the individual phases present in the films. Red shift and asymmetry of Raman mode characteristic for CuSe2 enable us to estimate nanocrystal dimension. In the analysis of the far-infrared reflection spectra, numerical model for calculating the reflectivity coefficient of layered system, which includes film with nanocrystallite inclusions (modeled by Maxwell–Garnet approximation) and substrate, has been applied. UV–VIS spectroscopy and photoluminescence spectroscopy are employed to estimate direct and indirect band gap of CuSe2.

The aim of the present work is to study influence of preparation method on samples characteristics, creation and behavior of surface optical phonons (SOP) modes with change of concentration of doping elements by micro Raman spectroscopy. Nanocrystalline samples of ZnO(Co) were prepared by use of traditional wet chemistry method followed by calcinations and the microwave assisted hydrothermal synthesis. The phase composition of the samples (ZnO, Co3O4, ZnCo2O4) and the mean crystalline size (14–300 nm) were determined using X-ray diffraction measurements. In this paper we report the experimental spectra of Raman scattering (from 100 to 1600 cm−1) for both type of samples. Main characteristic of experimental Raman spectrum are: sharp peak at 436 cm−1 and broad multi phonon structure at ~1150 cm−1, typical for ZnO; sharp peaks at 194, 482, 521, 618 and 691 cm−1 typical for Co3O4 and sharp peaks at 185, 475, 520, 610 and 690 cm−1 typical for ZnCo2O4 nanoparticles. The phonon of registered phase’s exhibit effects connected to phase concentration, while the SOP phonon mode exhibit significant confinement effect.

On Raman scattering spectra of nanocrystaline samples ZnO(Co) prepared by use of the microwave assisted hydrothermal synthesis, surface optical phonons (SOP) where observed in the range of 519 - 572 cm-1. The mean crystalline size (33 - 300 nm) as well as the phase composition of obtained samples (ZnO, ZnCo2O4) where determinate with X - ray diffraction measurements. These measurements aloud us to study the change of SOP modes position with crystalline size and how change in concentration of doping element CoO influence the change of SOP modes intensity.

Optical properties of p-type Zn1−xMnxGeAs2 for 0 ⩽ x ⩽ 0.078 were investigated by Raman spectroscopy at room temperature. Phonons of ZnGeAs2 are experimentally determined and they are in excellent agreement with those theoretically predicted. Existence of MnAs clusters was confirmed in the sample with the highest concentration of Mn. MnAs was found in α and β phases and their vibrational frequencies are obtained experimentally. Plasmon – two different phonons interaction in Zn1−xMnxGeAs2 is registered and analyzed.

Surface optical phonons (SOP) were observed in the range of 496–572 cm−1 on Raman scattering spectra of nanocrystalline samples of ZnO(Co) prepared by use of the microwave assisted hydrothermal synthesis and traditional wet chemistry method followed by calcinations. The phase composition of the samples (ZnO, Co3O4, ZnCo2O4) and the mean crystalline size (14–300 nm) were determined using X-ray diffraction measurements. The SOP phonon mode exhibit significant size confinement effect, while the phonons of registered phases exhibit effects connected to phase concentration.

Nickel ferrite (NiFe2O4) and manganese ferrite (MnFe2O4) have been prepared by a soft mechanochemical route from mixture of (1) Ni(OH)2 and α-Fe2O3 and (2) Mn(OH)2 and α-Fe2O3 powders in a planetary ball mill. The mixture was activated for varying duration. Soft mechanochemical reaction leading to formation of the NiFe2O4 and MnFe2O4 spinel phases were followed by X-ray di raction, Raman and infrared spectroscopy, scanning and transmission microscopy. The spinel phase formation was rst observed after 4 h of milling (case 1) and after 3 h (case 2) and its formation was completed after 25 h in both cases. The synthesized NiFe2O4 and MnFe2O4 ferrites have a nanocrystalline structure with a crystallite size of about 30 and 40 nm for cases (1) and (2), respectively. There are ve Raman and four IR active modes. In order to understand better the whole process of phase formation, the Mossbauer measurements were done.

Powdery nickel ferrite, NiFe2O4 has been obtained by soft mechanochemical synthesis in a planetary ball mill. Ni(OH)2 and Fe(OH)3 are used as initial compounds. This mixture was mechanically activated for 25h, uniaxial pressed and sintered at 1100°C for 2h. The phase composition of the sintered sample was analyzed by X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and Raman spectroscopy. Morphologies were examined by scanning electron microscopy (SEM). The electrical DC/resistivity/conductivity at different temperatures was measured using a Source Meter Keithley 2410. An Impedance/Gain-Phase Analyzer (HP-4194) was used to measure the impedance spectra (100Hz - 10MHz) at different temperatures. [Projekat Ministarstva nauke Republike Srbije, br. III 45003 i br. III 45015]

Manganese ferrite, MnFe2O4 have been prepared by a soft mechanochemical route from mixture of (a) Mn(OH)(2) and alpha-Fe2O3 and (b) Mn(OH)(2) and Fe(OH)(3) powders in a planetary ball mill. The mixture was activated for varying duration. Soft mechanochemical reaction leading to formation of the MnFe2O4 spinel phase was followed by X-ray diffraction, Raman spectroscopy, scanning and transmission microscopy and magnetization measurements. The spinel phase formation was first observed after 12 h of milling and its formation was completed after 25 h in both cases. The synthesized MnFe2O4 ferrite has a nanocrystalline structure with a crystallite size of about 40 and 50 nm respectively for cases (a) and (b). There are five Raman active modes. Measurements after 25 h of milling show magnetization values of 70.4 emu/g and 71.1 emu/g respectively for cases (a) and (b). In order to understand better the whole process of phase formation, Mossbauer measurements were done. (C) 2011 Elsevier B.V. All rights reserved.

The aim of the present work is to study the magnetic properties of ZnO(Fe) nanocrystalline samples prepared by two methods of synthesis. We have used the microwave assisted hydrothermal synthesis and traditional wet chemistry method followed by calcination. The detailed structural characterization was performed by means of X-ray diffraction and micro-Raman spectroscopy measurements. The dynamic magnetic properties were studied by means of AC susceptibility χ . The measurements were performed at small AC magnetic field with amplitude not exceeding 5 Oe and different frequency values (from 7 Hz to 9970 Hz). The AC susceptibility maxima have been found for in-phase susceptibility Re ( χ ) and for out of phase susceptibility Im ( χ ). We analyzed the observed frequency dependence of the peak temperature in the AC susceptibility curve using the empirical parameter Φ that is a quantitative measure of the frequency shift and is given by the relative shift of the peak temperature per decade shift in frequency, as well as Vogel–Fulcher law.

Nanocrystaline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characterized by X-ray diffraction to determine composition of the samples (ZnO, Fe 2 O 3 , ZnFe 2 O 4 ) and the mean crystalline size (8–52 nm). In this paper we report the experimental spectra of Raman scattering. Main characteristics of experimental Raman spectrum in 200–1600 cm −1 spectral region are: sharp peak at 436 cm −1 and broad two-phonon structure at ∼1150 cm −1 , typical for ZnO; broad structure below 700 cm −1 that has different position and shape in case of ZnFe 2 O 4 or Fe 2 O 3 nanoparticles. Low-frequency Raman modes were measured and assigned according to confined acoustic vibrations of spherical nanoparticles. Frequencies of these vibrational modes were analyzed in elastic continuum approximation, which considers nanoparticle as homogeneous elastic sphere.

Lanthanum and antimony doped barium titanate powders were prepared by polymeric precursors method through Pechini process. Obtained powder was pressed into pellet and sintering was performed at 1300 °C for 8 h. The formation of phase and crystal structure of BaTiO3 was carried out by XRD analysis, Raman and IR spectroscopy. Microstructure properties such as grain size distribution and morphology of sintered samples were determined using scanning electron microscope. Therefore, it was analyzed relation between grain size, structure and properties of obtained ceramics. Influence of La- and Sb-doping on barium titanate properties was discussed.

Pure and antimony doped barium titanate powders were prepared by polymeric precursors method through Pechini process, which was carried out as a three-stage process from organometallic complex. Obtained powder was pressed into pellets and sintering was performed at 1300 °C for 8 h with heating rate of 10 °C min-1. The formation of phase and crystal structure of pure and Sb -doped barium titanate was approved by XRD analysis, Raman and IR spectroscopy. The influence of Sb doping on microstructure of barium titanate ceramics was investigated by scanning electron microscopy. Therefore, the relation between grain size, structure and properties of the obtained ceramics was analyzed. Influence of Sb doping on barium titanate properties was discussed.

BaTiO3 ceramic powders were prepared by a complex method based on the Pechini type reaction route and mechanically assisted synthesis. In both ways BaTiO3 ceramics were sintered after 120 min on 1300 °C without pre-calcination steps. The crystal structure was investigated by the XRD, IR and Raman spectroscopy. The particle size and morphology of BaTiO3 were examined by XRD and SEM. The XRD results of powders indicate the formation of cubic phase of BaTiO3. It can be observed that in the case of Pechini process BaTiO3 powder is well crystallized but in the case of mechanochemistry process, significant amount of amorphous phase was detected. The sintered BaTiO3 ceramic sample prepared by Pechini process, shows the formation of tetragonal phase. However, IR and Raman spectrum showed a mixture of cubic and tetragonal for BaTiO3 obtained by Pechini process and tetragonal for BaTiO3 obtained by mechanically assisted synthesis.

Far-infrared reflection and Raman spectra of Hg1−xMnxSe (x ≤ 0.3) alloys were measured at room temperature. The analysis of the Raman spectra was made by deconvolution technique. The analysis of the far-infrared spectra was made by a fitting procedure based on dielectric function which includes spacious distribution of free carrier influence on the plasmon–phonon interaction. In spite of strong plasmon–LO phonon interaction, we found that the long wavelength optical phonon modes of these mixed crystals showed two-mode behaviour. The model of phonon behaviour was developed, and we obtain very good agreement with experimental results.

Raman scattering spectra of Pb1−xSnxTe (x = 0, 0.15 and 0.25) doped with Indium in the temperature range 10–300 K are presented. Three local modes of Indium at about 115, 155 and 190 cm−1 are registered. These modes are discussed in terms of local vibrations of impurities corresponding to different In charge states. The position of these lines is independent of alloy compound, temperature and amount of added In.

Nanocrystalline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characterized by X-ray diffraction to determine composition of the samples (ZnO, Fe2O3, ZnFe2O4) and the mean crystalline size (8–52 nm). In this paper we report the experimental spectra of the Raman scattering (from 200 to 1600 cm−1). Main characteristics of experimental Raman spectrum in 200 to 1600 cm−1 spectral region are: sharp peak at 436 cm−1 and broad two-phonon structure at ≈ 1150 cm−1, typical of ZnO; broad structure below 700 cm−1 that has different position and shape in case of ZnFe2O4 or Fe2O3 nanoparticles. PACS numbers: 63.20.−e, 78.30.Fs, 78.67.−n

Bismuth titanate, Bi4Ti3O12 powders were prepared by mechanically assisted synthesis from their oxides. The diameter of obtained particles depends on time of milling. In order to understand the grain size effects on the crystal structure we measured X-ray, TEM analysis and Raman spectra. The effect of mechanical treatment on the grain size is quite evident: as the milling time increases (3, 6, 12 h), the powder becomes more activated and grain size decrease (7.3, 7.2, 6.9 nm). With reducing the grain size, quantum effects at the Raman spectra, is reflected in the mode position change against balk crystal. And also, coagulation of each line appears, as well as a significant asymmetry of certain modes. (c) 2006 Elsevier B.V. All rights reserved.

This paper describes the structural and optical properties of Cu-Se thin films. The surface morphology of thin films was investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Formation of Cu-Se thin films is concluded to proceed unevenly, in the form of islands which later grew into agglomerates. The structural characterization of Cu-Se thin film was investigated using X-ray diffraction pattern (XRD). The presence of two-phase system is observed. One is the solid solution of Cu in Se and the other is low-pressure modification of CuSe2. The Raman spectroscopy was used to identify and quantify the individual phases present in the Cu-Se films. Red shift and asymmetry of Raman mode characteristic for CuSe2 enable us to estimate nanocrystal dimension. In the analysis of the far infrared reflection spectra, numerical model for calculating the reflectivity coefficient of layered system, which includes film with nanocrystalite inclusions (modeled by Maxwell -Garnett approximation) and substrate, has been applied. (C) 2016 Elsevier B.V. All rights reserved.

Bismuth titanate is a typical layer-structured ferroelectric material and belongs to the Aurivilius type-structure compounds family. A bismuth titanate ceramic material could be obtained by mechanically activated synthesis after thermal treatment at a temperature slightly lower than in conventional solid-state reaction. In this case bismuth titanate was prepared through mechanochemical synthesis starting from bismuth oxide and titanium oxide in rutile form. The mixture of oxides was milled in a zirconium oxide jar in a planetary ball-mill in intervals from 1 to 12 hours. The ratio of powders to zirconium oxide balls during milling was 1:20. Bismuth titanate was formed after 1 h. The Raman spectroscopy analysis was performed.

In this work we present galvanomagnetic measurements and Raman scattering spectra of Pb 0.75 Sn 0.25 Te + 1.2 at.% In. Positions and concentrations of different In impurity states are obtained using the Gibbs distribution and results of galvanomagnetic measurements. In Raman spectra, modes at about 90, 170, 340, 510 and 570 cm −1 were observed at all temperatures. These modes were discussed in terms of multiphonon emission (MPE) process on DX-like centers.

Pb 1-x M nx Te crystals were obtained by the Bridgman method and PbTe 1-x S x crystals were grown by the vapour-liquid- solid technique. The structural properties of Pb 1-x M nx Te (x ≤ 0.10) and PbTe 1-x S x (x ≤ 0.05) were observed by X-ray powder diffraction analysis. The optical properties were studied by Raman spectroscopy as a function of temperature. Measurements on these samples of different composition gave information about the Mn and S position in the lattice (off-centering), their clustering and ordering, as well as of the influence of these processes on the crystal structure and properties. The model of phonon behaviour based on the Random Element Isodisplacement model was applied, and it was found that the phonons in PbTe 1-x S x, show a two-mode behaviour (each TO-LO mode pair of the end members degenerates to an impurity mode), while the Pb 1-x Mn x Te optical phonons have a intermediate one-two-mode behaviour (the LO-mode frequency shifts continuously from PbTe to MnTe, while the other modes resemble the two-mode case).

In this paper, we used Raman spectroscopy and spectroscopic ellipsometry to investigate optical properties of plastically deformed copper. Chemically pure copper prepared in a sample of square cross section (10 × 10 mm2) and about 50 mm long was extremely plastically deformed with the repeated application of Equal Channel Angular Pressing. Information about microstructure with ultrafine grains is obtained by atomic force microscopy. The structure of the sample surface—the copper oxide and surface roughness over-layer—was registered by spectroscopic ellipsometry. By Raman spectroscopy, two types of lines are registered: narrow, with the width ∼7 cm−1; and wide, ∼40 cm−1, which implies that nano-sized crystal structures related to three-dimensional amorphous boundary spaces exist in the specimen.

In this paper, we used the Czochralski method to obtain good-quality yttrium aluminium garnet (Y3Al5O12)—YAG and yttrium aluminium garnet doped with neodymium—Nd:YAG crystals. The investigations were based on the growth mechanisms and the shape of the liquid/solid interface on the crystal properties and incorporation of Nd3+ ions. The obtained single YAG and Nd:YAG crystals were studied by use of Raman and IR spectroscopy. There are strong metal oxygen vibrations in region 650–800 cm−1 which are characteristics of Al–O bond: peaks at 784/854, 719/763 and 691/707 cm−1 correspond to asymmetric stretching vibrations in tetrahedral arrangement. Peaks at 566/582, 510/547 and 477/505 cm−1 are asymmetric stretching vibrations, and 453/483 cm−1 is symmetric vibration of Al–O bond in octahedral arrangement of garnet structure. Lower energy peaks correspond to translation and liberation of cations in different coordinations—tetrahedral, octahedral and dodecahedral in the case of the lowest modes.

In Part I of this paper, we used X-ray, far-infrared reflectivity and electron paramagnetic resonance measurements to investigate optical and magnetic properties of Hg1-xMnxSe (x≤0.26) alloys. In Part II, we expand our investigation to Raman spectroscopy and galvanomagnetic measurements. We registered two-mode behaviour of long wavelength optical phonons and described it by modified Genzel’s model. Except modes from the centre of Brillouin zone, there are some of forbidden modes in Raman spectra that originate from the edge of the zone, as well as a mode that corresponds to the maximum of phonon density of states. Modes of unalloyed α–MnSe are registered, too.

The influence of Mn concentration on Raman spectra of Pb1−xMnxTe (x ≤ 0.1) crystals at room temperature in 15–200 cm−1 spectral range were investigated. Well-resolved peaks at 129 and 146 cm−1 were observed for all samples. These modes originated from the vibrations of TeO2. Other modes appeared at about 53 and 104 cm−1 when x = 0.02. The intensity and position of these modes increases when Mn concentration increases. The analysis showed that off-centre Mn ions in Pb1−xMnxTe play important role in the Raman activity. The model of phonon behaviour based on Genzel's model was developed. It was found that the long wavelength optical phonon modes of these mixed crystals showed an intermediate one–two mode behaviour. Also, structural properties of the samples were observed by optical microscopy after chemical polishing and etching, and by X-ray diffraction.

Far-infrared reflectivity and Raman spectra of Cd1−xMnxTe1−ySey (x = 0.05, y = 0.11; x = 0.15, y = 0.1) single crystals were measured in the 40–300 cm−1 spectral range at 80 and 300 K temperatures. The analysis of the far-infrared spectra was carried out by a fitting procedure. We used a dielectric function that takes into account the existence of plasmon–LO phonon interaction. On that way the three optical mode frequencies (TO/LO pairs) at about 140/160, 170/190 and 205/210 cm−1 were obtained, depending on composition and temperature. In the Raman spectra we registered only the two first modes. We discussed these results in the frame of the model which we previously applied on Hg1−xMnxTe1−ySey. The agreement of the calculated phonon frequencies with experimentally determined ones is very good. We also present results of X-ray measurements.

Phonon spectra of Cd1-xMnxS (x = 0; 0.01; 0.05; 0.1; 0.15; 0.3) nanoparticles (d ~ 4.5 nm) have been investigated by far-infrared reflection (FIR) (spectral range 40 - 600 cm-1, temperature range 80 – 300 K) and Raman spectroscopy (100 – 700 cm-1, 300 K). Cd1-xMnxS nanoparticles have been synthesized by using aqueous solution precipitation. We obtained interesting features in FIR spectra: there are expected modes of bulk CdS (240 cm-1, 300 cm-1), new modes connected with nano-size of CdS (130 cm-1, 170 cm-1) and additional mode at 120 cm-1 in Cd1-xMnxS nanoparticles which can be assigned to the presence of Mn. The position of obtained modes is discussed in the frame of the linear chain model with both mass and force constant defects. Raman spectroscopy gives us only the mode at 300 cm-1 and its second harmonic.

Raman scattering spectra as well as results of galvanomagnetic, X-ray and ultrasonic measurements of PbTe 1− x S x ( x = 0.02 and 0.05) mixed crystals in the temperature range from 10 to 300 K are presented. A structural phase transition at about T c = 60 K for x = 0.05 was detected, whereas for samples with x = 0.02, the phase transition was not observed. The two TO/LO mode pairs of PbTe 1− x S x mixed crystals are determined from Raman spectra at all temperatures, and according to that we found that the optical phonon modes of these mixed crystals showed a two-mode behaviour. The model of phonon behaviour based on the model of Genzel et al. was applied. One additional mode, at about 75 cm −1 , the intensity of which is connected with off-center sulphur ions, is observed in all samples. Our results suggest that the only reason for complex phase transition in PbTe 1− x S x systems may be the off-center sulphur ions.

ZnS nanoparticles were synthesized mechanochemically by high-energy milling. In order to investigate influence off milling time to sample properties, samples were produced in three different milling times (5 min, 10 min and 20 min). The morphology of samples has been investigated by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). X-ray diffraction (XRD) investigation of synthesized nanocrystals identified cubic structure. From XRD, ZnS size of crystallites was estimated as 1.9 nm (after 5 min milling time), 2.3 nm (10 min) and 2.4 nm (20 min), implying that we are in strong confinement regime. The optical properties were studied by Raman spectroscopy, in spectral region 100-500 cm(-1), excitation source was 514.5 nm (E-L = 2.41 eV), which means that we are in off resonant regime. Dominant spectral structures, of comparable intensity, are registered in spectral region 130-180 cm(-1), around 265 cm(-1) and around 345 cm(-1). First two are assigned as second-order ZnS modes. A theoretical model of continuum medium was used to calculate frequencies of the confined optical phonons in ZnS. Satisfactory agreement with experimental results was found and mode at 345 cm(-)1 is assigned as LO type phonon confined in ZnS nanocrystal. (C) 2015 Elsevier B.V. All rights reserved.